Well, I used to work for Dynomax & I can assure you, a 2.5" version of the Super Turbo flows better than a 2.5" or 3" 2 chamber, 3 chamber, or Delta flow Flowmaster. The 3" Flowmaster versions had flow rates of around 350 scfm, while the 2.5" Dynomax Super Turbos have flow rates of around 410-420 scfm. Comparative OE mufflers have flow rates of usually under 200 scfm. I remember buying a pair of 16" bodied Chrysler "Hemi" mufflers from Mitchell Motors back in the early 80's - to replace the 20" bodied originals on my old '71 Hemi Charger. The mufflers from Mitchell flowed like CRAP - I could immediately tell they were restrictive. Back then I didn't know crap about exhaust. I should have installed a set of Walker Red Line Z mufflers, which evolved into the Super Turbos.

The big differences internally between a Dynomax Super Turbo & an OE muffler are two things: the size of the internal perf tubes, & the Super Turbos have flow directors (bank turns) at each end, & OE's do not, and most other performance mufflers won't either. If you buy a 2.5" in/out Super Turbo, it will have 2.5" flow tubes inside. An OE type muffler with 2.5" inlet/outlet, will usually have 2" dia internals. A CHEAP, crappy turbo muffler (like the Thrush California Boss Turbos) have 2 flow tubes internally & NO packing, plus the flow tubes are smaller diameter. Super Turbos have a fiberglass mat that wraps around the center section of the muffler (you can see it in the photo someone posted), but this mat breaks down in about a year or two, & the mufflers will get louder - especially the 14" ones. Some oval mufflers have two flow tubes, some have 3. The Super Turbos are GOOD turbo mufflers. The Dynomax Ultra-Flow mufflers are straight-through, & they do not "tune" the sound like Super Turbos do, so they sound different than each other. From a flow standpoint, the scfm of a 2.5" 14/20" Super Turbo offset/center is around 410, and a straight-through Ultra Flow is around 1100. There is a HUGE difference in flow, but do you really need the extra flow of the Ultra Flow? Only a few dyno runs could tell you. Bob Karakashian & many of the other guys running in the Pure Stock Drags are using the Dynomax Ultra Flows. Those WAAAAAY outflow flowmasters & all other non straight-through oval mufflers. The stainless Ultra Flows with the stock-style spun-locked heads, flow the same as the Dynomax race series welded construction mufflers - also now called Ultra Flows. The welded series are offered in bigger flowpath & bigger in/out than the stainless ones, so there is more variety. On a closing note, I don't know what the internals are like in the Accurate mufflers, & I don't know who is building them for them - I doubt they have the equipment to build them & especially fab the spun-locked heads. If they do, then that's impressive.

There are quite a few mufflers currently in the Dynomax & Thrush line that I suggested & partially designed. There were also ones that I tried to get them to bring to market, but was unsuccessful. One was reverse flow Super Turbos in 2.25" & 2.5" versions for AAR's & T/A's - the standard oval size but 20" long. *They currently offer these reverse flow mufflers, but they are only 14" long bodies - not long enough. Those were referred to as "fabricator" mufflers. I have been building my own chambered exhaust mufflers & mufflers for AC Cobras since 2002.

John,
747 is 2.25 in and out
and should be here by the end of the week

oh thats even worse , I thought I read it was 2.5 in ... need to get my glasses updated

Iam thinking of using 17747 2.25 super turbo mufflers, Do you know if they are necked down inside ( 2") ? or so ? Would the 20" case muffler have lless drone ? While I've got yo what about Quiet Flow SS, just how bad do the kill power ???

Iam thinking of using 17747 2.25 super turbo mufflers, Do you know if they are necked down inside ( 2") ? or so ? Would the 20" case muffler have lless drone ? While I've got yo what about Quiet Flow SS, just how bad do the kill power ???